Preheat the oven to 400ºF.
Line an 8 by 8 by 1 1/2-inch square pan with aluminum foil, allowing the foil to hang over the edges of the pan. Grease the pan with 1 teaspoon of butter. Place the nuts on a round cake pan and place in the oven. Toast until golden brown, about 6 to 8 minutes. If you shake the pan a couple of times in the oven, it helps for overall browning. Remove from the oven and cool.
In a 2-quart saucepan, over medium heat, combine the sugars, salt, vanilla, butter, and cream. Stir constantly until fully incorporated, about 1 minute. Bring the mixture to a boil and cook, stirring occasionally, until the mixture reaches 254ºF. (hard ball stage) on a candy thermometer, about 15 minutes after the mixture comes to a boil. Sprinkle the nuts over the butter of the prepared pan. Pour the sugar mixture over the nuts and place in a draft-free area and allow to cool completely. Place both chocolates in separate bowls over pots of simmering water. Stir occasionally until all of the chocolate is melted and smooth. Stir 1/4 teaspoon of the oil into each chocolate.
To temper the chocolates: Dip the bottom of each bowl of chocolate in a bowl of cold water and stir the chocolate until it begins to thicken. Immediately remove from the cold water and place back over the pot of simmering water. Stir over the hot water just long enough to make the chocolate liquid again. Remove the bowl from the heat. Set aside until ready to use.
Turn the caramel out onto a cutting board. Using a sharp knife, cut into 1-inch squares.
In a cool and draft-free area of you kitchen, dip half of the nut caramels in the semi sweet chocolate and the remaining in the milk chocolate, coating completely and shaking off the excess. Place the chocolates on a piece of parchment paper and allow let sit for a
couple of hours or until the chocolate sets. Place the chocolates on a serving platter and serve. They will keep for 1 week in an airtight container. Do not refrigerate.
Yield: about 4 1/2 dozen chocolates